The present application is the national stage under 35 U.S.C. 371 of PCT/IT98/00357, filed Dec. 10, 1998.
1. Technical Field
The invention relates to a continuous process for hyperactivation of fluids for sterilization.
Specifically but not exclusively the invention is usefully applied for the hyperactivation of sterilizing chemical agents of known type, such as hydrogen peroxide, peracetic acid, chlorine dioxide, hypochlorites, chlorates, oxidants based on brominexe2x80x94iodinexe2x80x94fluorine etc., intended to be subsequently used for sterilizing surfaces of any kind, such as paper, plastics, metal, organic material etc., belonging to various objects intended for the most varied fields of application, such as the food, pharmaceutical, medical, electronic industries.
2. Background Art
The above-mentioned substances have been used for sterilization for some time in that their sterilizing properties are well known. Moreover, the data (concentration, temperature and contact time) relating to their use in this kind of application is generally provided by the manufacturers themselves. Sterilization processes which employ the above-mentioned agents for sterilizing surfaces and containers of paper or multi-layer board for foodstuffs in particular have also been known for some time.
One of these processes teaches spraying a sterilizing solution onto the surface to be treated and then activating it by heating it up and causing evaporation thereof, obtaining active radicals, effective in the sterilization action, in direct contact with the surface to be sterilized.
Another of these processes teaches mixing the sterilizing solution with an inert gas and subsequently heating the mixture to obtain a gaseous vapour/inert gas mixture which is immediately blown onto the material to be sterilized, where the vapour condenses. This second process is described in U.S. Pat. Nos. 4,742,667 and 4,631,173.
Both these processes have the drawback of needing a high operating temperature in order to obtain a large number of active radicals, and cannot therefore be used for materials which degrade at moderate temperatures of the order of 50-70xc2x0 C. A further problem in the above-cited prior art processes is that the gaseous vapour/inert gas mixture which is obtained, given the high temperature, is very rich in active radicals but is not controllable; there is therefore virtually instantaneous combination among the active radicals, which tends to destroy or render uncertain the sterilizing power of the mixture. For this reason it is essential that the activated mixture is immediately brought into contact with the material to be sterilized. For this purpose, in the first process the gaseous mixture is obtained directly in contact with the material to be sterilized, whereas in the second process the material to be sterilized is in contact with the outlet zone of the evaporator. This clearly leads to serious limitations in terms of plant construction, in that the gaseous mixture has to be used in the same zone in which it is produced. The difficulty of controlling the gaseous mixture, together with the tendency of the active radicals to combine together, also increases the time required for reliable sterilization of the materials.
The main object of the invention is to eliminate the above-mentioned disadvantages by providing a process which enables a sterilizing gaseous mixture to be obtained which is rich in radicals, which are activated and uniformly distributed in the mixture and the chemical/physical state of which can be controlled for relatively long periods of time.
A further object of the invention is to provide a process which enables the gas production zone of the sterilizing gaseous mixture to be separated from the zone the of its use.
A further object of the invention is to provide a process which enables the sterilizing gaseous mixture to be obtained and used at temperatures which are moderate and in any event lower than the boiling point of the sterilizing solution. An advantage of the invention is that it enables the sterilizing gas mixture to be used to sterilize heat-sensitive materials.
A further advantage of the invention is that it reduces the operating costs and consumption of the sterilizing processes and reduces the residues of sterilizing agent on the treated surfaces.
A still further advantage of the invention is that it enables a sterilizing gaseous mixture to be obtained which reduces the sterilizing times of the treated surfaces. These and further advantages and objects are all achieved by the invention as it is characterized in the appended claims. Some substantially similar practical applications of the process are also described, the last of which involves a more detailed description aided by an illustration in the form of a drawing.